In case of stress caused by dimensional changes of the substrate of a pressure-sensitive adhesive sheet, or of the adherend to which the pressure-sensitive adhesive sheet is stuck, a problem arises in that the pressure-sensitive adhesive sheet ends up peeling from the adherend over time. Such stress must be absorbed/relieved with a view to solving that problem. A conceivable solution herein involves increasing the flexibility of the pressure-sensitive adhesive layer.
Conventional methods for imparting flexibility to a pressure-sensitive adhesive include, for instance, using a base compound having a low glass transition temperature (Tg), adding a low molecular weight polymer having a low glass transition temperature (Tg), adding a plasticizer (liquid component), or reducing the content of cross-linking agent (Patent Documents 1 to 3)
[Patent document 1] Japanese Patent Application Laid-open No. 2003-49143
[Patent document 2] Japanese Patent Application Laid-open No. H03-220120
[Patent document 3] Japanese Patent Application Laid-open No. 2004-099792